Eggplants do not splice properly.

[Geokinesis]

When you splice an eggplant seed with a seed of another plant, the hybrid plant's fruit doesn't contain any nicotine.

[Geokinesis]

I think eggplants are just fucked in general, even when increasing the potency through infusion you never get more that 4ish units of nicotine in an eggplant.